Well, I've spoken to Colin Molloy in Manchester. He's cleaned and polished a sax before!! Hoorah! And loads of other brass instruments. Cost-wise, to dip-strip in a mild caustic tank to remove the lacquer, then polish body, keys, rods, guards, as he did on the last one (another bargain buy of someone's who paid "£20 and a pack of lager" for it) it'll be £80-100.
As I'm a "regular" I'd think Colin will charge me the lower end £80. He is THE man in the gun trade for metal refinishing (Google "Colin Molloy Bluing") and I've always been absolutely amazed at his work for me.
Here's a rifle restoration I did with Colin's Bluing: http://www.picturetrail.com/sfx/album/slideshow/22262009
So, project looking good now as I know Colin's polishing will be fab. I discussed plating but he advises against this, both from his practical perspective of actually doing it, and also his advice that bare brass if looked after a little shouldn't develop horribly. He did offer caution about an individual's sweat and how this can vary in the way it affects the brass.
So.... £50 sax, £80 dip-strip & polish, £180 re-pad, postage £20 to/from Colin, petrol £20 to/from Geoff (he's near enough) = £350. Less sale of MP (if I can EVER get it off!), say, £50.
£300 for the whole project?